Man United went behind at St Mary’s when Graziano Pelle struck before goals from Anthony Martial either side of half time put them in the driving seat.
Juan Mata added a third for United before Pelle clawed a goal back for Southampton late on.
Van Gaal rubbished suggestions that his side had struggled during the opening exchanges against Southampton.
When asked whether United needed to score more goals to make up for a lacking defence, van Gaal said: “I don’t agree with you. Have you seen the goal average against?
“Also last season all the media was writing the defence is very bad but at the end we were third [least conceded] in the Premier League [United were fourth for goals against]. You say something and don’t think about what you are saying.”
United were poor from a defensive point of view on Sunday but van Gaal is right in saying that they have generally had a good record for a while now. Having a reliable and consistent back four helped enormously at the start of the campaign but Luke Shaw’s injury has forced a reshuffle, resulting in the haphazard display against Southampton. The new backline will have to put some hours in on the training pitch in order to get accustomed to one another.